Lean body mass vs Skeletal muscle mass

squashyhelen

This is entirely out of academic curiosity, but I was hoping someone can explain an interesting result I have observed since getting my fancy EatSmart Scale. Lean body mass (i.e., what's not fat) does NOT follow the same losses or gains for muscle mass. I assume this is because the muscle % the scale gives is based on skeletal muscle mass, i.e., voluntary muscles as opposed to the smooth muscles (intestines etc.) that make up lean body mass. This is after a lot of googling, and really, I have no idea if my understanding is right. Interestingly, there can be a LOSS of lean muscle mass while a GAIN in (skeletal?) muscle mass. What?

Here are the results:
Jan 15: Weight: 121.5lbs. Fat: 20.1% (24.42lbs --> thus 97.08lbs lean mass). Muscle: 39.7% (48.24lbs). Water 57.4% (35.06lbs).
Jan 25: Weight: 119.8lbs. Fat: 19.8% (23.72lbs --> thus 96.08lbs lean mass). Muscle: 40.5% (48.52lbs). Water 57.5% (35.48lbs).
Feb 6: Weight: 118.6lbs. Fat: 19.1% (22.65lbs --> thus 95.95lbs lean mass). Muscle: 41.5% (49.22lbs). Water 57.9% (35.50lbs).

So: Total Weight lost = 2.9lbs. Total Fat lost = 1.77lbs. Total Lean Mass lost = 1.13lbs. Total Muscle GAIN = 0.98lbs. Total water gain = 0.44lbs.

Isn't that weird? The results completely tickle my mind and academic curiosity. Which is why I am throwing this out there for you guys to figure out of course.

Sarauk2sf

Those scales are incredibly inaccurate tbh.

I did a write up here, which focused on BF - but the principles apply: http://www.myfitnesspal.com/topics/show/830595-body-fat-estimation-methods

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squashyhelen

Hmm that does make sense. I just thought that the lean muscle mass and skeletal should at least go in the same direction! Hope it's the scale's error in reading as opposed to losing "muscle" in intestines and organs and whatnot!

viajera99

The scales just measure body density...they can't tell the difference between muscle and water (much less different types of muscle!), for example, which is why if you are retaining fluid you will see your total weight go up and your BF % go down.

If you track it long enough you can see a trend, but 3 data points are really impossible to interpret with any accuracy. If you want to see an example of this, here is a link to my TrendWeight dashboard. https://trendweight.com/u/c7231261df6041/ Click on 3 months and Fat % at the top and you can see my BF % are all over the map (the dots), but only the trend line makes some sense.

Sarauk2sf

Hmm that does make sense. I just thought that the lean muscle mass and skeletal should at least go in the same direction! Hope it's the scale's error in reading as opposed to losing "muscle" in intestines and organs and whatnot!

I would put my money on the scale being wrong.

heybales

How many personal stats do you enter in to the scale? Gender, age, height, ect?

And it is only a foot BIA measurement, or hands too?

Just curious.

As mentioned, since only 1 thing is actually calculated from the measurements, the other stuff must be assumed off that and other stats.

And just as BMI is pretty worthless individual stat, their tables or formula's for what % of what is what could be too.

squashyhelen

@diver: your link is pretty amazing - it's really too bad you have to have one of their special scales to sign up for an account. Btw - congrats on that overall BF decrease! I'm aiming for the same and hoping to preserve muscle. Then got confused as to which figure I should be looking at (there is a muscle % figure that the scale gives).

@heybales: You enter gender, age, height, and also there's a separate setting for athletic males and females (which I'm not). It's only a foot BIA measurement but has actually been relatively consistent so far. I wonder how they calculate that muscle %! No amount of googling yields any answers. And if Sara puts her money on something, heck if I ain't going to believe what she says.

heybales

I just realized the other thing that was off perhaps.

LBM is indeed everything but fat, and includes all muscle.

So it is of course estimating water amount, which is part of LBM, but not a part of muscle, kind of.
It really is, as glucose and water is stored in the muscle and you might say are an integral part of it.

So it's calculating density and BF based on the amount of resistance, using formula using other stats to tighten that up.

Now since it has a estimate of BF%, the other part is LBM.

Now they apply another constant that some research probably says lets you divide muscle from water, probably again based on averages from your other stats and weight.

There's your difference between water and muscle.

I wonder if that other constant is as well tested as the 0.73 used for splitting out LBM?

Here's a nice BIA reference too.

http://www.brianmac.co.uk/fatbia.htm

viajera99

There's actually a sweet little work around if you want to use that site. Open up a fitbit account at fitbit.com --you don't actually need a fitbit to do so, and it's free. You can go to the track weight tab and enter your weights and body fat% manually. Then open up a TrendWeight acct and link the accounts on the TW website, and it will fetch your manually entered weights and BF% from fitbit and graph them for you.

squashyhelen

There's actually a sweet little work around if you want to use that site. Open up a fitbit account at fitbit.com --you don't actually need a fitbit to do so, and it's free. You can go to the track weight tab and enter your weights and body fat% manually. Then open up a TrendWeight acct and link the accounts on the TW website, and it will fetch your manually entered weights and BF% from fitbit and graph them for you.

YAY!! It's working!!! Can't wait to plug my numbers in and see that slow decrease! Thanks so much.

squashyhelen

I just realized the other thing that was off perhaps.

LBM is indeed everything but fat, and includes all muscle.

So it is of course estimating water amount, which is part of LBM, but not a part of muscle, kind of.
It really is, as glucose and water is stored in the muscle and you might say are an integral part of it.

So it's calculating density and BF based on the amount of resistance, using formula using other stats to tighten that up.

Now since it has a estimate of BF%, the other part is LBM.

Now they apply another constant that some research probably says lets you divide muscle from water, probably again based on averages from your other stats and weight.

There's your difference between water and muscle.

I wonder if that other constant is as well tested as the 0.73 used for splitting out LBM?

Here's a nice BIA reference too.

http://www.brianmac.co.uk/fatbia.htm

That is indeed interesting. Wonder what equation is used to separate out the muscle and water. Water is the only thing for me that has stayed pretty much constant. Also, I wonder if the amount of minerals in your body impact this as well... potassium and calcium are supposed to better conductors or something right? Increasing minerals might therefore change the readings?

Leonardo_Simo_Fuertes

For squashyhelen how do you calculate the total body water from The TBW percentage?

heybales

5 yr old thread, likely won't be noticed.

Also, did you read the whole thread, might have missed the comments of not knowing how it was done.